The Bat is Revealed to the Old World
(General POV)
Location the Chaos Wastes/The Fortress of the Damned, Main Chamber
In the frozen world, where time has been stopped by three all-powerful, and malignant entities from another dimension.
When a massive rift tore open, and a being clouth in daemonic grey armor and black fur cape with several skulls made his way through the rift, their name is Ixion Daemonhart, Avatar of All Chaos Gods, and lord of the Dark Legion that has risen in the Chaos Wastes of the Old World.
At the moment they step into the Old World, time continued to flow and all the lesser daemons began to move again, in the main chamber.
Sensing their Dark Gods appearing, stronger than a "moment" ago, as these daemons are connected directly to the Warp, and the Dark Gods that rule over it because of this they are the only beings in this world, able to easily sense the power, presences, and changes that happens to all three of the Chaos Gods within the avatar, Ixion Daemonhart.
Ixion's eyes flared crimson, as he instructed his daemons to continue fortifying and corrupting the fortress to their liking, in the end it seems that the Fortress of the Damned, shall become the main base or capital for their army, so they had to now personally empower it and mark it exclusively as their own, cause they thought of a brilliant plan involving the fortress, while back on the Warp...
The Warp Gods commanded their avatar to leave the main chamber, and travel outside of the fortress.
FLASHBACK...
Location the Warp-Above the Blood Lands, the Azure Moon's Core/Secret Azure Moon Altar of Ixion
As the trio of Chaos Gods sat down on their respected throne, of the Thrones of the Damned surrounding the altar of Ixion, they began channeling all their respected power, essences, and consciousness into the avatar.
Just like last time, and all the times Laharl has done the transfer into a avatar, the swirling, sphere dome of chaotic energies, acting as a barrier around the avatar was fading away and reappearing around Laharl, Khorne, and Nurgle, immediately when they finished they felt themselves back into their avatar and stronger then before with their artifacts Haz'kariot, the Axe of Rage, Bloodreaver and the Pandemic Star Shield bound within their avatar, as they stood tall and proud within their Ixion.
They were all eager to return and cause untold anarchy, mayhem, destruction and bloodshed.
Once back on the Old World, they'll use the Haz'kariot to bring fort all the reinforcements they've prepared for their army back on that world.
That's when Nurgle asked for a quick meeting within the "void" that Laharl put inside their avatar, both the Lord of Skulls and Lord of Darkness were curious about their younger brother's request so they did as he asked...
Location the Psyker Dimension within the Avatar/Ixion
The trio of Chaos God were in a dark alternative space, once again they three appeared as great shadows with Khorne being crimson eyed, Nurgle being lightsaber green eyed, and lastly Laharl being dark purple eyed.
Laharl was the first to speak, as he asked his brother the Plague God, "Where here as you requested Nurgle. So what is it that bothers you, brother?" Khorne while staying quiet, but completely agreed with what his older brother ask their younger sibling.
Nurgle first showed his brother appreciation for listening to him before he breathed in gasply and sickly before telling them the reasons he made them speak in the avatar "void" instead of outside.
The Plague God began to speak,"First...while here...in...the void...cause...no...time passes...making...this...meeting...relatably quick." Nurgle saw his brothers' shadow nod in acceptance to what he stated, as the Decaying God continued to speak, "I have...a...splendid idea...brothers!!! Laharl you...possess...some...Warp Tesseracts...still?" Laharl was confused but nodded to his brother question to give him some affirmation.
This made Nurgle smile and laugh as he told them his plans and why he asked the Dark One if he still possess some Warp Tesseracts/Free Absolute Creations...
Nurgle told them that they resolved their military issues for now in the Old World, all that was left was securing a proper base and start conquering territory for their own.
So he told them they can solve all their trouble by using the fortress that they already claimed and remake it into a literal mobile base, allowing them to have heavy support in battle from all the fortifications and armaments they put on the Fortress of the Damned, plus they can add more to the design to better serve them in the campaign not only the one their on currently, but also all future ones as well.
Both Khorne and Laharl, were shocked and impressed by their brother's idea...it's true not only will it solves every issue they may have now but also future ones as well, Laharl couldn't help but think about Malus Darkblade's campaign in the Total War games, receiving a great military boost against enemies with a Black Ark providing reinforcements and secondary army in the early game of the Darkblade Campaign, this mobile fortress could serve as their own "Black Ark"!!!
Now that the Dark One thought about it more, when they encounter Malus in the Old World, in exchange for freeing him of the Greater Daemon of Slaanesh, Tz'arkan, he can secure not only his loyalty but maybe create a new Dark Daemon Eldar faction under his service, which can influence and corrupt the eldars into faster debauchery which will also hasten the "Great Fall" of the Alderi, causing the birth of Slaanesh to be earlier, not only opening the Eye of Terror but also killing off majority of their enemies from the Alderi Pantheon.
Not only that once he claims Tz'arkan from Malus he can use the so called Drinker of Worlds as material for one of his future Elder Daemons, in lore Tz'arkan is considered one of the most powerful Slaaneshi Daemons, that could even challenge both Nkari and Shalaxi Helbane the Bloodthirster Hunter.
In the end both Khorne and Laharl have given their full support and approval of Nurgle's idea, making said Lord of Decay very bashful and happy as they discussed this "Mobile Fortress" idea in greater detail.
After some time offering ideas in the end, they agreed to create not only a mobile fortress, that will not carry all their resources, spoils, and reserved troop but also act as a walking tank of Chaos in all ways of expression, spreading all forms of corruptions, always expanding and growing, armed with all matter of defenses and weapons to aid their forces in battle.
They'll use Laharl's FGDCs which Khorne and Nurgle will believe its a Warp Tesseract, along with their own powers and corruptions to create a whole new greater daemon beast of Chaos Undivided, Khorne was pleased and eager to create such a loyal beast, while Nurgle was happy and excite to have a loyal pet like Karanak is to Khorne, when the Plague God said that comment Khorne went ballistic saying, "Do not compare my hound, to a meager pet Nurgle!!!! He is my loyal companion, and hunter not just some random creature living in a mortal home!!!!!" that's when Laharl said in a teasing tone, "So a dog. OK got it."
This of served to further infuriate the Blood God, as his brothers continue to tease and mess with him, but in the end they have fully agreed with the Plague God's plan and once they return to the Old World, and summon their reinforcements they'll turn the Fortress of the Damned into an actual Daemon of Chaos.
PRESENT TIME...
Location the Chaos Wastes/Outside of the Fortress of the Damned
Ixion commanded all his daemons and Norscan followers to gather outside the fortress, for the Gods have blessed them with great fortune and power.
Khorne and Nurgle even suggested to their brother to start introducing his corruption, and influence, this shocked the Dark One and even expressed that he was surprised by this and that their not expanding their own influence at the moment, even thou he suspects that is because this world was already under a weaker influence of their counterparts so it'll be but a slight inconvenience for them to assume control and gain many, many followers and warriors for their, and to the Dark One's educated guess he was spot on.
That was exactly what they told him, so during this speak him and his brother started mentioning of another Dark God, calling him the "Dark One", "Dark Harbinger", "Valboga", "One that Dwells in the Void", and Laharl even added a new name that he expects the Norscan to call him for now on "The Bat" since Khorne is the Hound, Nurgle is the Crow, Tzeentch is the Raven, and lastly Slaanesh is the Serpent, than he'll take the bat as his moniker in northmen's pantheon.
As Ixion/Warp Gods expressed that their eldest brother and leader within their body is a champion of the Bat, Laharl even letting Laharl take the reigns to transform the avatar into his state.
Taking the appearance of a violet colored armored, as the Norscan saw their Chaos Lord with purple glowing eyes has a long pointed forehead horned helmet with a long burgundy knight plume on top, his daemonic greatsword turn violet, burgundy, and black color with razor-sharp edges with curves, hooked spike, serrated spikes, and what appears to be a daemonhead (Mark of Carnage) as the guard of the Hellbane.
Seeing and sensing this it was clear that their lord was telling the truth, a fifth Chaos God that none has heard about until now, with this the worship and influence of Laharl will to spread and bring fort followers to serve in their conquest and corruption of the entire Old World.
At the same time, as time was now flowing and Ixion had left the cover of the Void that once covered the fortress.
Allowed the Gods of the Realm of Chaos, to finally find and hear all said by their aspiring champion this revelation both shocked and annoyed the four of them, they could barely stand and show a meature of respect to Ultnarth, the Rat God of the Skaven.
Last thing they need is another rival to be added to their constant struggle and fighting over the Realm of Chaos, and the realms of mortals.
This has doubled each of the Chaos Gods efforts to fully claim Ixion Daemonhart, and all the souls he harbors into their individual service!!!
As the Gods were watching closely, wanting to know more of this "pretender" Laharl that is claiming a soul of their champion, Ixion reverted to his Chaos Undivided state and reached down to the right side of his waist.
They held up a diamond daemonic crystal talisman or emblem that not even the Four Chaos Gods knew of such artifact, Ixion/Warp Gods said, "This is the Haz'kariot. A blessing and gift from the Bat, Laharl, God of Carnage, Infernals, Oblivion, Darkness, and Creation!!! With this relic, we're able to open a rift into our old world, into the domain of Chaos and summon more neverborn to serve under us!!!! BEHOLD!!!!!"
While they kept the Haz'kariot in the air it turned from a diamond to a ruby, pointing the artifact to their right the Haz'kariot wailed opening a rift into...the Blood Lands, and several khornate daemons (29 bloodletters and 50 flesh hounds) came through the rift, kneeling before Ixion/Khorne within Ixion, shocking all both mortal and dark divine at the power of the Haz'kariot!!!
OW-Khorne was the most shock and in truth slightly annoyed, but their "Chosen" was far from done.
As they commanded the new additions to their khornate roster, to join their previous bloodletters, Ixion/Warp Gods closed the rift to the red infernal, war-striken daemonic land of Khorne (Warp), now the Haz'kariot changed from a ruby to a jade.
Once again wailing and opening a rift into, the Garden of Nurgle, bringing fort slightly over a hundred plaguebearers that slowly made their way through the rift, and like blood daemons before they cheered, grunted, and swung their plagueswords into the air in reverence to Ixion/Papa Nurgle inside of Ixion.
Like before the Plaguebearers were commanded to join the other nurglish forces of plague marauders infectors, infected hosts (warhounds & norscans) as they close the rift and once again the Haz'kariot changed crystal...from jade, to amethyst.
One last time the Haz'kariot wailed and open a rift that none have seen or heard about before a violet nightmarish land, that exuded with Carnage, Lust, Madness, and much more this realm drew all the four Chaos Gods as now they believe that this Laharl might be one of their kin, hidden from another world as the strange daemons alongside more brown skinned elves, that Tzeentch, OW-Nurgle and Slaanesh clamored for came through, (2 infernals, 31 mortifinis and 200 frost eldars) greeting their God's avatar and with that the Dark Legion as the Norscan have started to call, Ixion's forces has reached above 1000 in number.
The Four Chaos Gods, were now more intrigued and have a greater desire to claim Ixion as their own, especially since it meant a direct connection to this Laharl's domain, but also easier and direct connection to across the world even equalling their other champion, Wulfrik and his enchanted vessel the Seafang, which is capable of crossing vast distances through the Realm of Chaos using its daemon-enchanted figurehead.
But the Four Chaos Gods haven't seen everything yet, let alone a meager of what the Trio of Warp Gods have at their disposal.